EXTRACTION  OF  ZIRCONIA 


BY 


OGDEN  LIVERMORE 


THESIS 


FOR  THE 


DEGREE  OF  BACHELOR  OF  SCIENCE 


IN 

CHEMICAL  ENGINEERING 


COLLEGE  OF  LIBERAL  ARTS  AND  SCIENCES 


UNIVERSITY  OF  ILLINOIS 


1922 


1922 

L 75 


UNIVERSITY  OF  ILLINOIS 


THIS  IS  TO  CERTIFY  THAT  THE  THESIS  PREPARED  UNDER  MY  SUPERVISION  BY 


.QGJ3EH_JLI_VEmOEE. 


ENTITLED EXTRACT  I Cj_i_  _0F_  JJJR£ONIA 


IS  APPROVED  BY  ME  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR  THE 


degree  OF 


Instructor  in  Charge 


Approved 


HEAD  OF  DEPARTMENT  OF Ch.e_i.St  rjT 


500206 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/extractionofzircOOIive 


TABLE  OP  CONTENTS 


History 

1.  Discovery 

2.  Experiment  in  Uses 

Commercial  Uses 

1.  Refractory 

2.  Enamel  and  Glass 

3.  Miscellaneous 

Occurrence 

1.  Relative  quantity 

2.  Forms  and  Regions 

Purification  methods  from  the  Literature 

1.  Attempted  methods  and  points  of  failure 

2,  Patented  method 

Method  Developed  and  Used 

1.  Basic  principle 

2.  Procedure 

3.  The  product 


Summary 


1 


EXTRACTION  OP  ZIRCONIA 

I 

HISTORY 

Zirconia  was  not  discovered  very  early  in  history  on 
account  of  its  similarity  in  reaction  to  alumina  and  other 
earths.  In  1789  Klaproth  determined  its  existence  with  cer- 
tainty. He  reported  that  in  the  Jargon  of  Ceylon  he  had  found 
31.5  per  cent  of  silica,  0.5  per  cent  of  iron  and  nickel  ox- 
ides, and  68.0  per  cent  of  some  new  earth.  A few  years  later 

♦ 

he  identified  the  same  material  in  the  Hyacinth  of  Prance. 

In  1797  GO^ton  de  Morveau  confirmed  the  work  of  Klaproth. 

At  about  the  same  time  Vauquelin  gave  this  new  earth  the  name 
Zirconia  and  described  some  of  its  compounds.  In  1798  Iromms- 
dorff  tried  to  reduce  Zirconia  to  Zirconium  and  failed,  but 
in  1824  Berzelius  perpared  the  impure  metal  and  two  years  lat- 
er had  a sample  of  sufficient  purity  to  determine  the  atomic 
weight.  After  this  many  mistakes  were  made  by  chemiftts  who 
thought  that  they  had  found  a new  oxide  when  in  reallity  they 
had  only  a mixture  of  Zirconia  and  some  of  the  rare  earths 
that  occur  in  the  same  minerals.  These  mistakes  were  due  to 
the  difficulty  and  length  of  the  processes  for  the  isolation 
of  Zirconia  and  its  great  similarity  to  the  rare  earths  in 
action  and  appearance. 

Baddeleyite,  the  impure  native  Zirconia,  was  dis- 
covered in  1892  by  two  different  men  working  independently 
in  two  different  regions.  Hussak  found  it  in  Brazil  aid  call- 


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ed  it  brazilite  and  at  about  the  same  time  Fletcher  found  it 
in  Ceylon  and  called  it  baddeleyite.  Hussak  retracted  in  fa- 
vor of  Fletcher. 

It  was  not  until  about  1913  or  1914  that  any  exten- 
sive work  was  done  on  Zirconia  in  regard  to  its  practical 
value.  It  was  used  to  some  extent  before  this  in  Drumond 
lights  to  replace  the  calcuim  oxide.  The  more  recent  inves- 
tigations bring  out  its  value  as  a refractory  in  many  ap- 
plications. A Siemeus-Martin  furnace  in  a steel  works  at 
Remscheider,  Germany  was  actually  operated  with  a Zirconia 
lining.  The  lining  was  in  good  condition  after  four  months 
of  use  and  statistics  from  the  test  showed  a saving  of  fifty 
per  cent  in  maintenance  cost.  It  has  also  been  found  that 
the  use  of  Zirconia  is  advantageous? in  the  metallurgy  of  cop- 
per, steel,  bronze,  and  red  brass  for  it  does  not  absorb  them 
or  become  weakened  by  the  action  of  the  molten  metals  or  their 
oxides.  In  these  various  uses  it  has  been  found  necessary  to 
use  some  binding  material  with  the  Zirconia  for  it  cannot  be 
fused  together  at  temperatures  available  at  present;  no  doubt 
furnaces  to  fire  it  could  be  developed  if  it  were  more  plenti- 
ful. Sodium  silicate,  starch,  phosphonic  acid,  glycerine, 
tar,  and  borates  have  been  used.  Articles  made  with  these 
binders  have  a specific  gravity  of  about  five.  This  weight  is 
objectionable  in  some  cases  and  it  has  been  found  that  some 
material  such  as  sawdust  or  ammonium  salts  added  before  fir- 
ing will  cause  porosity  and  consequent  lightening  of  the  ob- 
ject, This  porosity  would  be  detrimental  for  uses  where 


3 


liquids  or  gasses  were  concerned  "but  does  not  lower  the  re- 
fractory power  of  the  Zirconia. 


4 


II 

COMMERCIAL  USES 

Thus,  Zirconia,  the  oxide  of  zirconium,  has  been  found 
valuable  and  wellsuited  for  a number  of  purposes.  The  great 
drawback  to  its  extensive  use  is  the  fact  that  a small  parr  cent 
of  impurity,  especially  of  iron,  greatly  reduces,  if  not  complete-1 
ly  destroys,  its  value.  It  has  been  produced  in  the  pure  condi- 
tion by  many  methods  but  these  methods  have  always  been  slow, 
too  expensive  for  commercial  use,  and  not  easily  adaptable  to 
large  scale  commercial  productions.  The  problem  is  to  find 
some  method  that  can  handle  sufficient  quantities  at  a cost  low 
enough  so  that  the  Zirconia  can  be  produced  in  large  amounts 
profitably. 

There  is  an  extensive  market  for  a low  priced  pur 
Zirconia  in  the  field  of  refractory  materials.  It  makes  good 
quality  furnace  linings,  combustion  tubes  and  boats,  crucibles, 
casting  molds,  pyrometer  tubes.  The  pure  Zirconia  fuses  at 
approximately  3000°  C. , and  does  not  volatilize  below  this  tem- 
perature. The  most  nearly  pure  native  material  can  endure 
only  1300°.  1.0  per  cent  of  iron  will  reduce  the  melting 

point  of  the  pure  oxide  from  3000°  c.,  to  2500°  C.  The  articles 
of  Zirconia  have  a very  low  coefficient  of  expansion,  8.4  x 10“^, 
so  that  they  can  be  quenched  suddenly  from  high  temperatures 
and  will  withstand  wide  variations  in  temperature.  It  has  been 
discovered  that  where  as  quartz  ware  does  not  remain  constant 
in  structure  but  has  transition  points  and  gradually  becomes 
crystalline,  the  Zirconia  ware  has  no  transition  points 


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and  is  more  durable.  Its  property  of  low  heat  conductivity 
goes  well  with  its  high  melting  point  in  furnace  linings  or 
wherever  a retention  of  heat  is  desired.  As  furnace  lining 
it  lasts  several  times  as  long  as  ordinary  lining  material  for 
its  reaction  with  strongly  acid  or  basic  slags  is  very  slow. 
Fluorides  and  bisulphaties , and  carbon  in  the  electric  furnace, 
are  the  only  materials  which  tend  to  destroy  it  rapidly.  It 
is  practically  impervious  to  liquids,  and  combustion  tubes 
are  gas  tight  up  to  1000°  C. 

In  addition  to  the  foregoing  uses  pure  Zirconia  is 
valuable  as  a constituent  in  glass  and  enamels  as  an  opaci- 
fier.  Many  other  salts  of  zirconium  that  are  used  in  medi- 
cine, in  sizing  silks,  in  dyeing,  in  fire  proofing  cloth, 
and  others  are  made  by  starting  with  the  pure  oxide.  The  im- 
pure oxide  is  used  relatively  extensively  at  present  but  it 
must  not  be  confused  in  value  with  the  purematerial,  for  the 
latter  would  be  much  better  in  nearly  every  case.  Many  of 
these  uses  are  minor  and  the  impure  oxide  is  used  because  of 
its  low  price.  The  uses  briefly  enumerated  merely  outlines 
the  beginning  of  the  commercial  possibilities  for  Zirconia. 


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Ill 

OCCURRENCE 

The  element,  zirconium,  occurs  in  the  earth* s crust 
in  many  forms  and  although  it  is  only  fairly  abundant  it  is 
quite  widely  distributed.  An  estimation  of  the  amounts  of 
the  more  abundant  oxides  shows  Zirconia  to  exist  to  the  extent 
of  0.03  per  cent  in  the  crust.  Its  relative  quantity  can  be 
judged  from  comparison  with  the  quantities  of  other  better 
known  oxides  and  elements: 

C02-  --------  0.49# 

CL2 0.06# 

S ....  0.11# 

FeQ 2,63# 

MgO  --------  3.92# 

Ha20  3.46" 

ZrO 2 ————————  0.03# 

It  is  found  most  commonly  combined  in  the  minerals; 
zircon,  a zirconium  silicate;  baddeleyite,  sometimes  known  as 
brazilite,  the  impure  native  oxide;  zirkite,  a mixture  of 
forms  of  zircon  and  baddeleyite;  and  zirkelite,  a mixture  con- 
sisting of  baddeleyite,  zircon,  and  a silicate  differing  from 
zircon  in  composition  and  structure.  Of  these  four  the  badde- 
leyite is  the  most  important  from  the  stand  point  of  commer- 
cial use.  The  silicate  ores  are  more  difficult  to  break  down 
and  do  not  contain  as  high  a percent  of  Zirconia. 

Baddeleyite  is  found  in  Brazil,  the  United  States, 


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Ceylon,  Sweden,  and  Italy.  The  most  pure  ore  comes  from  Cey- 
lon but  the  deposits  in  Brazil  are  more  extensive  and  workable. 
The  other  deposits  are  not  used  to  any  appreciable  degree. 

The  deposits  in  North  Carolina  reached  a maximum  yearly  pro- 
duction of  four  tons  in  1905.  In  Brazil  the  deposits  are  of 
two  types,  the  alluvial  pebbles  containing  90.0  to  93.0  per 
cent  Zirconia  and  the  ore  proper,  zirkite,  containing  some 
zirconium  silicate  and  the  equivalent  of  80.0  to  85.0  per 
cent  Zirconia.  Due  to  its  content  of  more  easily  decompos- 
ible  silicate,  and  of  native  Zirconia,  and  its  occurrence  in 
the  same  region  zirkelite  is  mined  with  the  zirkite.  The 
boulders  and  large  masses  are  too  hard  to  drill  for  explosives 
and  must  be  broken  by  the  primitive  method  of  heating  the  rock 
and  then  shattering  it  by  sudden  cooling. 

The  silicate,  zircon,  is  also  used  but  to  less  extent 
and  more  often  for  gems  and  certain  cutting  tools  than  for  re- 
fractory material.  It  is  found  in  the  United  States,  the  Ural 
Mountains,  Greenland,  Norway,  Transylvania,  Bohemia,  the 
Tyrol,  France,  Italy,  Australia,  New  Zealand,  and  in  rather 
small  amounts  ih  many  places. 

There  are  many  other  minerals,  some  of  high  Zirconia 
content,  which  are  of  little  value  either  because  of  their 
occurrence  in  non-workable  quantities  or  because  of  the  diffi- 
culty of  their  decomposition  and  purification.  The  follow- 
ing list  gives  only  those  numerals  which  contain  at  least 
20  per  cent  Zirconia: 1 


V 


. 

. 


8. 

MINERAL 

COMPOSITION 

PER  CENT  ZR02 

Adelfolith 

Weathered  Zircon 

47.42 

Anderbergite 

(Si02)i2*^3H20 

41.20 

Anerbachite 

Weathered  Zircon 

55.18 

Baddeleyite 

Native  Zirconia 

up  to  99.0 

Beccarite 

Zircon  with  Ca  & Fe 

62.15 

Brazilite 

sec  baddeleyite 

80.0 

Cataplerite 

H2(Na2Ca)Zr  Si3  0X1 

30.-40.0 

Cyrtolite 

Weathered  Zircon 

36.-61.0 

Elpidite 

Na2  Si205*Zr  (Si205)2 

20.50 

Eudialyte 

Na13(Ca  Fe)g  (Si  Zr)2(j°  §| 

10.-20.0 

Hiortdahlite 

Zircon  Pyroxene 

21.5 

Lovenite 

(Si°03)2Mn  Ca  Fe*(ZrOF)Na 

30.0 

Oliveiraite 

3Z  r 02*2Ti  02*2  Hg  0 

63.36 

Orvillite 

8 Z r 02*6  Si  02  5 H20 

71.83 

Polymignite 

Metazirconotitanate 

14.-30.0 

Pyrchlor 

Niobate  - titanate 

20.0 

Tachyaphaltite 

Weathered  Zircon 

39.0 

Uhligite 

(ZrTi)  05*Ca  ♦ ( Ti  A1)0&A1 

22.0 

Wohlerite 

Si  Zr  Na  0 F • Ca  Na 

10  3 2 42  3 10  5 

15.-23.0 

Zirlcelite 

Zirconium  silicate 

50.0 

These 

names  given  to  the  various  minerals 

of  zirconium 

are  often  confusing  for  different  men  have  used 

them  at  differ- 

ent  times  to  mean  different  materials.  This  confusion  in  the 

names  must  be 

remembered  when  statements  in  the 

literature 

seem  to  be  contradictory  or  ambiguous. 

9 


IV 

PURIiFI  CATION  - METHODS  FROM  THE  LITERATURE 

Now  with  these  main  facts  of  Zirconia  in  mind  the  next 
step  is  its  extraction  and  purification.  There  are  numbers  of 
methods  given  in  the  literature  but  only  those  which  treera  to  be 
distinctive  and  to  give  promise  of  practability  will  be  consi- 
dered here. 

There  are  two  main  ways  to  extract  the  Zirconia  from 
the  ore,  upon  which  all  methods  for  the  production  of  the  pure 
material  depend.  In  the  case  of  an  ore  such  as  baddeleyite  con- 
taining a high  per  cent  of  the  oxide  the  leaching  method  is  us- 
ed. The  ground  ore  is  leached  with  acid,  usually  hydrochloric, 
which  dissolves  the  Zirconia  and  also  metallic  impurities, 
notably  iron,  and  leaves  the  silica  and  gangue  behind.  This 
gives  an  impure  solution  of  Zirconium  chloride.  The  second  class 
of  methods  is  more  difficult  to  carry  out.  It  consists  of  fus- 
ing the  ore  with  some  fluxing  material  to  get  a soluble  compound 
of  zirconium.  This  method  is  used  where  the  ore  contains  sili- 
cates and  other  insoluble  zirconium  salts.  Some  of  the  fluxes 
used  in  the  various  procedures  are  sodium  carbonate,  sodium  car- 
bonate and  silica,  or  niter  cake.  Where  sodium  carbonate  or 
sodium  carbonate  and  silica  is  used  a mixture  of  sodium  silicate 
and  sodium  zirconate  is  produced.  Upon  leaching  with  water  the 
silicate  dissolves  and  the  zirconate  is  hydrolyzed  to  give  a 
precipitate  of  zirconium  hydroxide,  and  as  before,  mixed  with 
metallic  impurities,  the  most  objectionable  of  which  is  iron. 


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10 


This  hydroxide  is  then  filtered  off  and  dissolved  in  acid  giv- 
ing an  impure  zirconium  salt  solution.  The  material  from  the 
niter  cake  fusion  i8  leached  and  the  silica  filtered  out.  This 
solution  is  nearly  neutralized  with  sodium  carbonate  and  zir- 
conium hydroxide  precipitated  by  the  addition  of  sodium  thiosul- 
phate at  boiling  temperature.  The  precipitate  is  filtered  and 
washed;  the  washing  removes  much  of  the  iron.  Then  the  dried 

cakes  can  be  ignited  for  an  impure  Zirconia  or  redissolved  in 

. - 2 
acid. 

There  is  another  type  of  acid  solution  method  where 
hydrofluoric  acid  or  fluorides  are  used  to  effect  the  solution 
of  the  zirconium  compounds.  Some  of  these  methods  accomplish 
their  purpose  very  well  but  are  not  practical  for  large  pro- 
duction of  Zirconia  on  account  of  the  cost  of  and  difficulty  in 
the  handling  of  the  hydrofluoric  acid  used  or  generated  during 
the  process.  Some  work  has  been  done  recently  in  the  electric 
furnace  in  the  line  of  breaking  down  zirconium  ores  and  obtain- 
ing a pure  compound  but  the  results  are  rather  uncertain  and 
the  process  is  expensive. 

Now  having  obtained  a crude  zirconium  salt  solution, 
it  is  necessary  to  remove  the  impurities.  According  to  methods 
given  in  the  literature  this  can  be  accomplished  satisfactorily 
in  many  ways.  No  attempt  will  be  made  to  describe  all  of  the 
methods  that  are  recommended.  A number  which  seemed  to  be  the 
more  practical  were  tried  and  found  to  fail  at  some  point  or 
to  be  unsatisfactory  in  some  other  respect. 


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11 


First,  there  is  the  method  of  precipitating  zirconium 
hydroxide  from  an  almost  neutral  solution  of  the  chloride  by  the 
introduction  of  sodium  thiosulphate  at  boiling  temperature. 

Here  the  iron  and  similar  impurities  are  supposed  to  stay  in  so- 
lution while  the  hydroxide  of  zirconium  is  filtered  off. 

2Na2S203+  4 H20  + Zr  Cl4  — 2S  + Zr  (OH)  4 + 2H20  + 2 S02+4  Na  Cl 

In  attempting  to  run  this  method  it  was  found  impossi- 
ble to  neutralize  the  acid  solution  sufficiently  for  the  thiosu- 
lphate to  work  without  causing  the  zirconium,  iron  and  others  to 
precipitate  before  any  thiosulphate  was  added. 

If  the  solution  is  made  faintly  alkaline  after  the  iron 
is  all  reduced  to  the  ferrous  state  and  three  times  the  weight  of 
the  oxides  present  is  added  in  tartaric  acid,  the  zirconium  should 
not  come  down,  and  by  passing  hydrogen  sulphide  into  the  solution 
at  60°C.,  the  iron,  nickel,  cobalt,  manganese,  zinc,  and  uranium 
that  maybe  present  are  precipitated.  The  precipitate  is  allow- 
ed to  settle  and  filtered  off.  The  hydrogen  sulphide  and  tar- 
taric acid  can  be  removed  by  boiling  to  dryness  with  sulphuric 
acid  and  nitric  acid,  adding  the  nitric  near  the  end.  The  ma- 
terial obtained  is  zirconium  sulphate.  In  trying  to  run  this 
method  it  was  found  that  the  tartanic  acid  would  not  keep  the 
zirconium  in  solution  when  the  solution  was  made  alkaline. 

Another  one  of  the  methods  given  uses  sulphur  dioxide 
or  fresh  sulphurous  acid.  The  hydrochloric  acid  solution  is 
neutralized  with  ammonia  until  the  precipitate  no  longer  goes 


12 


into  solution  with  boiling;  then  hydrochloric  acid  is  added 
drop  by  drop  until  the  precipitate  just  goes.  Then  the  solution 
is  boiled  with  excess  fresh  sulphurous  acid  or  sulphur  droxide 
gas  direct.  The  zirconium  should  come  down  leaving  the  iron 
and  impurities  in  solution.  Since  appreciable  amounts  of  am- 
monium chloride  prevent  the  operation  of  this  method  it  does 
not  work  well.  In  trying  this  method  it  was  found  that  the 
sulphur  dioxide  caused  no  precipitation. 

It  is  claimed  that  a mixed  solution  of  zirconium  chlo- 
ride and  ferric  chloride  in  strong  hydrochloric  acid  can  be 
separated  by  the  use  of  ether.  But  experiment  showed  that  the 
ether  takes  the  iron  and  some  zirconium  leaving  the  zirconium 
and  some  iron.  It  might  be  possible  to  get  an  almost  complete 
separation  of  the  two  chlorides  by  sufficient  repetition  of 
the  process  but  judging  from  trials  the  method  is  not  at  all 
satisfactory. 

Another  method  given  is  based  on  the  fact  that  the  dry 
chlorides  of  iron  and  zirconium  are  volatile  at  different  tem- 
peratures 30  that  theoretically  a-:: separation  can  be  made  on  this 

| 

basis.  Hydrochloric  acid  gas  and  chlorine  are  passed  over  the 
oxides  of  the  two  metals  at  200°  C.  The  iron  is  volatilized 
and  carried  away  while  the  zirconium  is  left  behind.  From  trial 
it  was  found  that  this  method  would  work  quite  well  if  certain 
mechanical  difficulties  could  be  overcome.  It  was  not  possible 
to  bring  the  gas  into  contact  with  all  particles  of  the  mater- 
ial and  the  ferric  chloride  condensed  in  the  cooler  regions  of 
the  combustion  tube.  The  method  could  not  be  made  to  work 


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13. 

successfully  with  the  equipment  at  hand.  However,  the  ferric 
chloride  was  partially  removed  to  the  back  of  the  tube.  The 
original  sources  of  these  methods  seem  to  be  unknown  or  at  least 
uncertain  in  all  cases. 

There  is  a patented  method  for  producing  pure  zirconia 
that  was  not  given  a trial.  The  solution  of  zirconium  and  im- 
purities as  chlorides  is  adjusted  to  a certain  acidity  and 

3 

heated  under  pressure  Zirconium  Hydroxide  comes  down. 


< . 


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t ' 


14. 


METHOD  DEVELOPED  AND  USED 

The  method  finally  used  to  produce  Zirconia  has  not 
been  found  to  appear  in  the  literature  but  there  is  no  certain- 
ty that  it  has  not  been  used  before.  It  depends  on  compara- 
tively simple  and  well  known  primciples.  The  basis  of  the  meth- 
od depends  on  the  fact  that  zirconium  hydroxide  can  be  preci- 
pitated from  an  acid  solution  of  ferrous  and  zirconium  chlor4 
ides  without  the  precipitation  of  the  iron.  The  solution  must 
be  kept  in  the  reduced  condition  for  as  soon  as  oxidation  occurs 
the  iron  will  come  down;  ferrous  hydroxide  is  soluble  while 
ferric  hydroxide  is  insoluble. 

The  ore  treated  was  a mixture  of  baddeleyite  and  some 
zirkite  from  Brazil.  Its  exact  composition  was  not  known  but 
can  be  judged  approximately  from  the  composition  of  the  two 
main  mineral  constituents.^ 


CONSTITUENT 


BADDELEYITE 


ZIRKITE 


Zr  02 

96.52-97 

.19 

93.18-68.93 

Si  o2 

.19- 

.70 

1.94-26.30 

Ti  02 

0- 

.48 

.36-  3.12 

EegOj 

• 41  — 

.92 

.43-10.26 

ai2°3 

. 0- 

.43 

0-  1.0 

Mn  0 

Trace 

0-Trace 

H2° 

i 

00 

CM 

. 

.39 

0-  1.56 

Ca  0 

0 - 

.55 

Mg  0 

0 - 

.1 

Alkalies 

0 - 

« 

to 

----- 

15 

In  the  purification  the  main  effort  was  directed  to- 
ward the  elimintation  of  the  iron  for  the  other  impurities  ex- 
ist in  small  quantities,  some  are  eliminated  at  various  points 
in  the  process,  and  none  "but  the  iron  have  been  found  to  he 
particularly  objectionable  in  the  Zirconia. 

Since  the  zirconium  was  present  in  silicate  as  well 
as  in  the  oxide  it  was  decided  to  use  the  fusion  method  of 
extraction.  The  fluxed  used  were  sodium  carbonate  and  silica. 
These  were  tried  mixed  in  different  proportions.  It  was  found 
that  a charge  consisting  of  30  g.,  of  finely  ground  ore, 

20  g.  of  silica,  and  250  g of  sodium  carbonate  in  two  of  the 
ordinary  fire-clay  crucibles  available  for  assaying  gave  the 
most  satisfactory  fusion  from  the  stand  point  of  complete  fusi- 
bility, quiet  fusion,  and  not  excessive  corrosion  of  the  crucible. 
Other  charges  of  30  g.  of  ore,  10  g.  of  silica,  and  250  g.  of 
sodium  carbonate;  of  30  g.  of  ore,  or  5 g.  of  silica,  and  of 
250  g.  of  carbonate;  and  also  one  higher  in  silica  consisting 
of  30  g.  of  ore,  25  g.  of  silica,  and  250  g.  carbonate  were  tried 
Those  charges  low  in  silica  were  fiund  to  remain  unfused  up  to 
temperatures  nearly  as  high  as  those  in  the  assay  muffles  about 
900°  to  1000^  C,  when  suddenly  they  would  melt  and  unless  cooled 
considerably  without  delay  would  bubble  up  violently  causing 
the  material  to  be  lost.  Hence  they  required  more  attention 
than  the  charge  containing  twenty  grams  of  silica  and  gave  a 
no  less  viscous  fusion.  The  charge  higher  in  silica  did  not 
fuse  well.  Five  of  the  charges  containing  thirty  grams  of  ore 
were  prepared  so  that  one  hundred  and  fifty  grams  of  the  ore 
was  started. 


' 


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* 

• 

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• ' 


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■ 


16 


After  pouring  and  cooling  the  fusion  was  crushed  to 
about  one  hundred  and  fifty  mesh  and  put  to  leach  with  water 
for  several  days,  the  liquior  being  poured  off  from  time  to 
time  and  the  residue  stirred  up  with  new  water*  A total  of 
about  ten  liters  of  water  was  used  for  three  successive  leach- 
ings.  This  leaching  must  be  thorough  for  any  sodium  silicate 
left  in  the  material  will  cause  trouble  when  acid  is  added 
later;  it  foims  the  gelatinous  silicic  acid  and  clogs  the  filter 
The  residue  now  is  chiefly  zirconium  hydroxide  and  its  impuri- 
ties, and  a small  amount  of  some  rock  gangue  which  did  not 
decompose  in  the  fusion.  All  possible  leach  liquor  is  drained 
off  and  hydrochloric  acid  is  added  to  dissolve  the  zirconium 
hydroxide.  This  solution  should  be  well  diluted  to  facilitate 
filtering.  The  small  amount  of  gangue  mentioned  above  is  fil- 
tered off.  It  was  found  that  eight  or  ten  layers  of  cheese 
cloth  in  the  Buchner  funnel  made  the  best  filtering  mednim. 

Now  the  solution  of  chlorides  must  be  reduced  to  al- 
low the  precipitation  of  the  zirconium  without  the  iron.  This 
is  accomplished  by  means  of  a simplified  Jones  reducing  column. 
A glass  tube  of  about  two  inches  diameter  and  three  feet  in 
length  is  filled  with  granulated  zinc.  A tube  leads  out  of  the 
stopper  at  the  bottom;  no  nitrogen  filled  container  is  used. 
Above  the  stopper  is  first  a Iyer  of  broken  glass  tubing,  and 
then  a layer  of  glass  wool;  these  materials  keep  the  five  par- 
ticles of  zinc  from  entering  the  tube  or  gathering  at  its 
mouth  and  stopping  the  flow  of  liquid.  Before  using  the  column 
to  reduce  the  solution  it  is  well  to  run  some  acid  through  to 


. 


: 

, 

• 

. 

. 

' 

, 


. 


■ 


* ■ 


. 


■ 


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, 

' 

. 

' 


17 


carry  off  or  dissolve  the  very  small  particles  of  zinc  that 
would  otherwise  be  carried  into  the  solution  and  raise  its  zinc 
content  unnecessarily.  This  is  especially  true  when  the  column 
is  not  freshly  filled  and  has  been  standing  for  some  days.  The 
impure  solution  of  zirconium  chloride  is  quite  strongly  acid 
and  must  be  adjusted  to  proper  strength  to  go  through  the  re- 
ducer. The  acidity  must  be  sufficient  to  cause  complet  reduc- 
tion during  two  or  three  passages  through  the  tube  and  yet  not 
so  strong  as  to  cause  violent  evolution  of  hydrogen.  When  the 
acid  is  too  strong  it  not  only  dissolves  unnecessarily  large  a- 
mounts  of  the  zinc  but  the  excessive  hydrogen  formed  rises  in 
the  column  and  prevents  the  rapid  flow  of  the  solution  down- 
ward; the  process  is  slowed  up.  As  the  solution  comes  from 
the  reducing  column  it  is  run  into  a glass  cylinder  about  six 
inches  in  diameter  and  twenty-four  inches  in  height.  The  dimen- 
sions are  not  essential  but  the  precipitate  will  settle  better 
for  washing,  as  will  appear  later,  if  the  vessel  used  is  tall 
and  relatively  narrow,  ^hen  reduction  is  complete  the  solution 
will  be  clear  and  colorless. 

It  is  necessary  to  keep  air  away  from  the  solution  as 
much  as  possible  to  avoid  reoxidation.  Therefore,  the  cylinder 
should  have  some  form  of  air  tight  cover.  The  zorconium  is  pre- 
cipitated in  this  cylinder  with  ammonium  hydroxide;  it  was  found 
to  be  best  to  have  the  ammonia  solution  in  the  cylinder  first 
and  run  the  zirconium  into  it.  There  seemd  to  be  less  tei  d- 
ency  toward  reoxidation  and  precipitation  of  the  iron,  probably 
due  to  the  fact  that  the  ammonia  fumes  would  displace  much  of 
the  air  from  the  cylinder  when  given  an  opportunity.  The  am- 


. 


' 


■ 


' 


. 


. 


4 

. 


.. 


. 


. 

. 


raonia  solution  reoxidizes  the  iron  to  some  extent  anyway  and 
this  must  be  due  to  air  carried  in  the  ammonia  solution.  Bet- 
ter results  might  be  obtained  if  liquid  ammonia  were  used. 

Zinc  hydroxide  from  the  zinc  of  the  reducer  column  comes  down 
at  the  same  time  as  the  zirconium  but  redissolves  in  an  excess 
of  ammonia  and  is  carried  away  in  the  washing.  The  precipi- 
tate is  allowed  to  settle;  then  the  liquid  is  siphoned  off  care 
fully  so  as  not  to  lose  any  of  the  zirconium  hydroxide.  The 
hydroxide  is  washed  a number  of  times  with  recently  boiled  dis- 
tilled water.  The  distilled  water  contains  too  much  air  as  it 
comes  from  the  tap.  Each  time  the  wash  is  siphoned  off  after 
the  precipitate  has  settled.  After  three  or  four  washings 
the  wash  is  tested  for  iron.  When  there  is  little  left  the 
washing  is  discontinued  and  the  hydroxide  is  redissolved  and 
reduced  as  before,  using  care  to  have  the  acidity  adjusted  cor- 
rectly for  the  column.  Precipitation  and  washing  are  repeat- 
ed. This  cycle  of  operations  must  continue  until  no  reaction 
for  iron  is  obtained  from  a solution  of  a little  of  the  zir- 
conium hydroxide  taken  from  testing.  An  average  of  six  repeti- 
tions was  found  necessary.  The  repeated  solution,  reduction, 
precipitation,  end  washing  of  the  zirconium  hydroxide  is  neces- 
sary on  account  of  its  light  and  bulky  nature.  It  holds  much 
solution  in  the  particles  of  precipitate  so  that  thorough  wash- 
ing is  impossible.  Finally  the  zirconium  hydroxide  is  filtered 
from  the  liquid,  dried,  and  ignited  to  Zirconia.  Time  became 
short  so  that  all  the  ore  started  was  not  run  completely  through 
but  it  is  estimated  that  the  yield,  would  be  about  fifty  grams 


■ 


. 

. 


< 


19 


of  Zirconia.  The  largest  loss  during  the  process  occurs  in  the 
amount  of  material  that  sticks  to  the  crucibles  after  fusion. 

If  the  processes  of  reduction,  precipitation  and  wash- 
ing were  carried  out  in  closed  vessels  and  the  liquid  transfer- 
red from  one  place  to  another  in  tubing  so  that  there  would  be 
no  contact  with  air  there  would  not  be  necessity  for  as  many 
repetitions  of  this  purifying  process.  In  working  with  open  ves- 
sels and  pouring  solutions  through  the  air  some  reoxidation  oc- 
curs and  must  be  corrected  the  next  time.  Absolutely if on  free 
Zirconia  could  not  have  been  produced  by  this  method  for  a 
geometrically  decreasing  fraction  of  the  iTon  always  remains. 
However,  the  material  is  very  nearly  pure  white  and  gives  none 
of  the  common  reactions  for  iron. 


■ 

' 

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■ 


. 


VI 


£0 


SUMMARY 

Zirconia  was  discovered  in  1789  and  from  then  until 
about  1912  or  1914  it  was  studied  quite  widely  but  was  used 
commercially  to  a small  extent.  Beginning  about  1912  or  1914 
more  extensive  investigations  of  it  properties  were  carried  out 
and  it  was  found  to  be  valuable  for  a number  of  uses  especially 
as  a refractory.  It  is  available  in  large  quantities  for 
0.05  per  cent  of  the  earth* s crust  is  Zirconia.  Deposits  occur 
in  nearly  all  parts  of  the  world.  These  deposits  are  chiefly 
the  native  Zirconia  or  Zirconium  silicates. 

In  the  attempts  made  to  extract  Zirconia  it  was  found 
that  a number  of  methods  that  are  reputed  to  be  satisfactory 
would  not  work,  A method  was  developed  in  which  the  zirconium 
is  precipitated  as  the  hydroxide  Y/ith  ammonia  from  a reduced 
hydroehloric  acid  solution  leaving  the  chief  impurities  in 
solution.  The  hydroxide  is  ignited  to  Zirconia. 


V 

■ 

, 

V 

. 

, 

. 


2* 


1.  Zirconium  and  its  Compounds  ------  F.  P.  Venable 

2.  Mineral  Foote-Notes  - - July  & August,  1918  - - - Bradford 

3.  C.  A.  10  - 255  - - - U.  S.  Patent  1,158,769 
Separation  of  Iron  from  Zirconia  ------  Askenasy 


4.  Mineral  Foote-Notes 


March  1918 


..  - 


. . 


. 


- • 


22 

REFERENCES 


Arnold  - - Zirconia  J.Soc. Chem.Ind . 37  - 743A 

Rodd  - - - Zirconia  as  a Refractory.  J.S.C.I,  37  - 213, 

Wedekind  and  Lewis  ------  Preparation  and  Properties  of 

Impure  Metallic  Zirconium. 

C.  A.  4 - 1434 
Annalen  371  - 366  - 88 

Bayer  - - - Preparation  of  Vessels  from  Zirconia 
C.A.  4 - 1527 

Z.  angew.  Chem.  23  - 4858 

Hi eke  - - - Use  of  Brazilian  Zirconium  Carrying  Earth  as  a 
Repractory. 

C.A.  2 - 1746 
Sprechsaal  41  - 214-5 

Meyer  - - - Zirconia,  a New  Ref ractory. 

Met.  & Chem.  Eng.  12  - 791 

Ruff,  Lieferfield,  and  Bruschke  - - - Work  in  the  Region  of 

High  Temperature  Zeit.  fur  Anorg.  Chem.  86  - 389. 

Askenasy  - -U.  S.  Patent  No.  1,158,769 
C.A.  10  - 255 

Arnold  - - -Zirconia;  Properties  as  a Refractory. 

Chem.  Ztg.  42  - 413,  426,439. 

Barnes  - - Use  of  Zirconia  as  a Mordant 
J.  Soc.  Chem.  Ind.  15  - 240. 

Baskerville  - Separation  of  Zirconium  from  Iron  by  S Og 
J.  Am.  Chem.  Soc.  16  - 475 

Berthier  - Preparation  of  Zirconia. 

Ann.  Chim.  & Phye.  (2)  50  - 362 

Berthier  - Separation  from  Iron  by  Sulphurous  acid. 

Ann.  Chim  & Phys.  (3)  7-74 

BoMhm  - - - Technical  uses  of  Zirconia. 

Chem.  Ztg.  35  - 1261 

Knorre  - - Separation  of  Zirconium  from  Iron  by  means  cf 
nitrosonaphthol. 

Z.  Angew.  Chem.  17  - 641 


2 3 


Meyer  - - - Refractory  Properties  of  Zirconia. 

Chem.  & Met.  13  - 263 

Podsyus  - - Melting  Zirconia  and  forming  Ware. 

C.A.  11  - 2838 
Z.  Angew.  Chem.  30  - 17. 

Leuchs  - - Pure  Iron  free  Zirconia. 

C.A.  10  - 375. 

German  Pat*  285,  344. 

Campbell  and  Caray  - Separation  of  Zirconium  from  the  Earths 
C.A.  10  - 1918 
U.S.  Pat.  1,182,880 

Coley  - - Zirconia  for  Industrial  Purposes. 

C.A.  14  - 1018 

Chem.  Trade  Jour.  65  - 742. 

Dantsizen  - Zirconia  in  Porcelan  Manufacture. 

C.A.  14  - 2403 
U.S.  Pat.  1,343,040. 

Deverean  - Zirconia  as  a Refractory. 

C.A.  14  - 2246 

Chem.  Trade  Jour.  66  - 567. 

Dreissen  - Influence  of  Zirconia  on  the  Properties  of  enamels. 
C.A.  13  - 2115 
Chem.  Weekblad  16  - 865. 

Griffiths  - Zirconia  as  an  Insulator. 

C.A.  11  - 3403. 

Trans.  Par.  Soc.  12  - 207. 

Barton  - - -Preparation  of  Zirconia  from  Ore. 

C.A.  14  - 3301. 

U.S.  Pat.  1,351,091. 

Bradford  - Zirconia  as  a Refractory  material. 

C.A.  12  - 1340 

Chem.  Trade.  Jour.  62  - 284. 

Andley  - - Zirconia  as  Refractory  Material. 

C.A.  11  - 3107 

Trans.  Eng.  Ceram.  Soc.  16  9 121 

(Anonymous)  Zirconia  Enamel 
C.A.  6 - 1665 
Ceramique  14  - 204 

Foote  Mineral  Company  - - Mineral  Foote-Notes  for:  March  1918 


24 


March  & April  - - 
Nov*  & Dec.  - - - 
May  & June  - - - 
July  & August  - - 

Browning  - -Introduction  to  the  Barer  Elements 
Phillips  - Minerology. 

S.  I.  Levy  - Bare  Earths. 

Martin  - - Industrial  Inorganic  Chemistry. 

Schoeller  and  Powell  - Analysis  of  Minerals  and  Ores 
Barer  Elements. 

F.  P.  Venable  - Zirconium  and  its  Compounds. 


1919 

1919 

1920 
1918 


of  the 


